Vehicles often accumulate odors inside their cabins during their lifetime of use. Such odors can be caused in a variety of ways and by a variety of sources. For example, objects left inside the vehicle, volatile organic compounds (VOCs) from the cabin interior materials, activities such as smoking and eating and the accumulation of dust and other pollutants suspended in the air can all contribute to the accumulation of odors. Eventually odors inside a vehicle become annoying and in some cases they may become a health risk if the source of odor involves bacteria, mold (fungi) or other microorganisms.
Besides the obvious surfaces that become contaminated with pollutants, like the seats, dashboards, carpets and other visible parts of the interior of a vehicle there are some hidden areas that create a perfect environment for pollutants, such as fungi, to accumulate and grow to a level where they can be noticed by smell even before they are visible. There are also many germs, bacteria and mold (fungi) that are present and are odorless.
One location for the growth and/or accumulation of hidden pollutants is in the interior of the air conditioning system. Typical air conditioning units include a chamber, where the refrigerant serpentine, also known as evaporator core, is embedded. Under normal operating conditions of a properly functioning air conditioning system, the serpentine condenses the moisture coming into the chamber due to the interaction between temperature, the existing dew point, and the relative humidity inside and outside the vehicle. In this process, the air entering the system contacts the cold interior parts of the system which retain and condense the humidity from the air. The cooler drier air comforts passengers once it exits the system, vents, and enters the vehicle cabin.
The condensation causes water to flow along the walls of the serpentine and the evaporator as well as the inside of the ventilation system. The accumulated water exits the chamber through a drain hole/hose designed specifically for this purpose. However, the surfaces inside the unit and ventilation system can remain humid for extended periods of time that vary from minutes to months depending on usage and climate conditions.
Year after year the air conditioning system is turned on and off and suspended dust, dirt, pollen, mold (fungi), bacteria and other polluting agents in the air enter the chamber passing into the evaporator chamber as the air conditioner blower draws air through the system both from the cabin and from the exterior of the vehicle through the air intake. Some of the particles from the polluted air adhere to the moist surfaces of the serpentine or other internal walls of the chamber as the air passes through the evaporator. In addition, some of the pollutants pass through the system and can become deposited over the interior surfaces of the cabin. The accumulated particles on the moist surfaces of the evaporator provide an environment in which micro-organisms can grow, particularly in the absence of UV light from the sun. The growth of microbial pollutants inside the evaporator further increases the amount of pollutants and odors that can enter the cabin in the airflow created by the blower. Automobile manufacturers have recognized a need for cleaning air conditioning systems for years. For example, U.S. Pat. No. 5,385,028 to General Motors discloses what is said to be a method of eliminating odor in a heat pump system of a vehicle that includes the steps of detecting removal of the vehicle passengers and ignition key after use of the cooling mode or air conditioning of the passenger compartment heat exchanger, operating the blower, reversing the flow of refrigerant in the heat pump to place the passenger compartment heat exchanger in heating mode to remove latent moisture. U.S. Pat. No. 5,259,813 to Mercedes discloses a method for deciding whether to recirculate air. The quality of the external air is determined by means of a pollutant sensor. The quality of the internal air is determined by calculation taking account of the air quantities introduced from outside into the internal space. A decision between air supply operation and air recirculation operation is then made on the basis of a comparison of the air qualities inside and outside. The pollutant sensor is preferably located in a casing whose internal space is accessible to gases through an opening which is preferably sealed by a gas-permeable membrane to eliminate odor. The proliferation of carbon air filters in new vehicles provides an indication of the consumers awareness of the air space in a vehicle and their desire for cleaner air. Even the US military has needs for air quality of cooled air as evidenced by U.S. Pat. No. 5,386,823.
Contaminants and odors can also originate from inside the passenger compartment and these also can circulate through the ventilation system and inside the evaporator when the air conditioner is operating. As an example, tobacco smoke originating from within the passenger compartment can cause odor in fabric headliners, upholstery and carpets all of which can be transported through the ventilation system and inside the evaporator. Further, any moisture accumulations in any part of the cabin can provide a place for mold and bacteria to grow. The mold can generate spores that can become suspended in the air inside the cabin. These spores can then re-circulate through the air conditioning system. Because of the moisture and temperature activity inside the evaporator and the lack of light, many of these contaminants and particles tend to accumulate inside the evaporator unit, creating layers of what appears to be “mud”. When the air conditioning is turned on spores in the system can be blown out into the cabin which can actually create a health risk in certain individuals. At best, this situation creates an annoying bad-smelling odor every time the A/C and/or the heater are turned on.
Methods for removing or treating these mold, bacteria and odors inside the evaporator and ventilation system have been developed. One method is to spray a foaming aerosol solution through the evaporator drain hole. The foam then expands into foam inside the evaporator. However, the rapid expansion from an aerosol to a foam state prevents the foam from effectively reaching the upper recesses of the evaporator. In addition, the method is complicated by the need to either remove the evaporator or raise the vehicle on a lift in order to reach the drain hole, or drill a hole in the evaporator case to allow a straw type aerosol injector access. These are all labor intensive operations requiring a person to position the vehicle appropriately, position and hold the aerosol can while depressing the valve releasing its contents.
Another method involves spraying a non-foaming aerosol solution into the exterior-located air intake, while the blower motor is running. However, because the aerosol droplets of the spray are heavier than air, and significantly larger at about 40-100 microns in size. They do not travel effectively and far enough to reach the inside of the evaporator or the entire ventilation system. Neither of these solutions is designed to treat interior cabin surfaces for micro-organisms and contaminants and both are labor-intensive in that the operator must continuously depress the valve on the aerosol can in order to release it's contents. Airsept, Inc. provides one such product. Alternatively, electronics can be used to keep the evaporator dry. See e.g., U.S. Pat. Nos. 5,899,082 and 6,840,051.
Other methods for treating odor-causing contaminants involve generating a vapor out of a cleaning solution inside the passenger compartment. Spray devices for carrying out this process can be pointed into the intake(s) of the air conditioning re-circulating system of the vehicle while the air conditioning system is in operation. The vapor-saturated air then circulates through the evaporator and the ventilation system, the cleaning solution can condense on the inside walls of the evaporator and vents and can flow into the passenger compartment. As this happens, the cleaning solution comes into contact and interacts with contaminants, thus removing or reducing mold, bacteria and odors. Another factor for treating is the volume of solution put into a passenger cabin over a given time. There needs to be enough surface time for the effectiveness of any solution and time of getting the solution into the compartment in a minimum amount of time.
Several methods are known for vaporizing a cleaning solution. In one method a vapor is created by using an ultrasonic piezo-transducer. However, such devices have a number of drawbacks in the automobile cleaning environment such that they have not been used in the past. For example, existing devices require a high voltage alternating current (AC) to operate, which places limitations on the application of these devices, as they are dependent on this type of power being available in close proximity in order for a vehicle to be serviced with this device and method. AC-powered devices of this nature are limited to areas of a building or shop with access to AC electricity. Ultimately, the current required to produce a sufficient amount of vapor from such a device has led manufacturers away from making portable systems.
Several devices operated by high voltage alternating current are known. For example, Wynn's AIRCOMATIC® Ultrasonic Air Conditioning Cleaning System. Wynn's AIRCOMATIC II® Ultrasonic Heating, Ventilation & Air Conditioning Cleaning System, which uses ultrasonic technology but needs to be connected to high AC voltage. The VAPORTEK® Restorator uses electric heat, but no ultrasonic technology and is powered by either AC or low voltage direct current (LVDC) in different versions. The AIRCLEAN-EVAPORATOR® which uses same technology as the VAPORTEK® Restorator, but is only powered by a high AC voltage version and the Wurth EVAPOclean®, which uses ultrasonic technology but requires high voltage AC power supply.
Each of these devices requires an electrical cable, or extension cord, that extends from an AC power source to the unit which is positioned inside a vehicle for use. The cable or cord transits through the vehicle's window or door. The vehicle window or door must be shut tight against the cord in order to minimize external air contaminants from entering the vehicle and not allowing the treatment to exit the vehicle. However, the thickness of the cable or cord leaves a gap to external air in the vehicle compartment which decreases the effectiveness of the service as a portion of the mist escapes through the gap. Moreover, the resulting pressure exerted from the window or door on the cable or cord can be sufficient to cut or strip insulation material and expose live wires that can lead to a short circuit and potentially a fire since these devices work with High AC Voltage. For these reasons such devices have not come into popular use.
For a piezoelectric transducer to operate properly, it is important that the liquid that is converted to vapor will not damage the device by corrosion, scaling or accumulation of residues. Since the device is meant to be used by a diverse group of people, there is the potential that different cleaning solutions may be used, either accidentally or deliberately, in the device. All of the known products allow for any type cleaning solution or chemical to be used, providing no control over what is used in the unit. This makes it highly likely that eventually the unit will be damaged by an unsuitable cleaning solution or be made unsafe to the occupants by someone using a commercially available cleaning solution like Windex, Febreeze, bleach or chlorine. The refill openings of known devices are even big enough to drop solids into the machine that will affect its performance. This is yet another reason why such devices are not widely used for cleaning automobile ventilation systems.
Some of the existing devices are configured in such a way that the turbulence, foam and/or splashing created by the piezoelectric transducers inside the “misting” chamber soaks some special mechanisms or components in the fluid, affecting their performance and durability of the device. Some devices have a level measuring system that signal the machine to stop when the fluid is low. The splashing and turbulence in these devices can in some instances create false signals stopping the device prematurely. In some cases the foaming and turbulence can also affect the amount of mist coming out of the device.
The vaporizing performance of a piezoelectric transducer is dependent on the amount of fluid over it and this is influenced by the angle of tilt of the device. Since existing devices don't have any way to orient the user on whether the equipment is really in an upright position, the performance of the equipment may be affected negatively without the knowledge of the user. For example, when the machine includes a level sensor and the machine is tilted a number of degrees from the horizontal, the machine may either work longer, which would damage the piezoelectric transducers if the level goes too low on one side; or the machine may stop its cycle earlier, which causes an insufficient amount of fluid use in the treatment.
The existing devices require close monitoring to ensure that treatments are finished and that machines are working properly. Most of the known devices display such information on their sides, which means that to monitor them in an automobile, the door of the vehicle must be opened and the technician must lean over and check the side of the device for that information.
For all of the above reasons known devices have not come into widespread use and new devices and methods for cleaning automobile ventilation systems are needed.